Eathquake Engineering .pptx

Basics Of Earthquake Engineering

1. Dr. NEERAJ KUMAR, PhD (IIT Roorkee) D e p a r t m e n t o f C i v i l E n g i n ee r i n g , Central University of Haryana, Mahendergarh, India E.mail: [email protected]

2. What are Earthquakes? The shaking or trembling caused by the sudden release of energy Usually associated with faulting or breaking of rocks Continuing adjustment of position results in aftershocks

3. What is the Elastic Rebound Theory? • R e i d ’ s ( 1906 ) e x p l a i n s h o w energy is stored in rocks R o c k s b e n d u n t i l t h e strength of the rock is exceeded Rupture occurs and the rocks quickly rebound to an undeformed shape Energy is released in waves that radiate outward from the fault

4. The displacement in a field occurred along the fault after California (1905) earthquake

5. The Focus and Epicenter of an Earthquake • • The point within Earth where faulting begins is the focus, or hypocenter The point directly above the focus on the surface is the epicenter

6. Seismographs record earthquake events At convergent boundaries, focal depth increases along a dipping seismic zone called a Benioff zone

7. Where Do Earthquakes Occur and How Often? ~ 80 % o f a l l e a r t h q u a k e s o cc u r i n t h e c i r c u m - P a c i fi c b e l t most of these result from convergent margin activity ~15% occur in the Mediterranean - Asiatic belt remaining 5% occur in the interiors of plates and on spreading ridge centers more than 150,000 quakes strong enough to be felt are recorded each year

8. Seismic Zones in India IS: 1893(Part 1) 2016, Criteria for Earthquake Resistant Design of Structures, Bureau of Indian Standards (BIS), New Delhi.

9. The Economics and Societal Impacts of EQs Damage in Oakland, CA, 1989 • • • • Building collapse Fire Tsunami Ground failure

10. What are Seismic Waves? Response of material to the arrival of energy fronts released by rupture Two types: Body waves Primary wave and Secondary wave Surface waves Rayleigh wave and Love wave

11. Body Waves: P and S waves Body waves P or primary waves fastest waves travel through solids, liquids, or gases c o m p r e ss i o n a l w a v e , material movement is in the same direction as wave movement S or secondary waves slower than P waves travel through solids only s h e a r w a v e s - m o v e material perpendicular to wave movement

12. Surface Waves: R and L waves • Surface Waves Travel just below or along the ground’s surface Slower than body waves; rolling and side - to - side movement Especially damaging to buildings

13. How is an Earthquake’s Epicenter L ocated? Seismic wave behavior P waves arrive first, then S waves, then L and R Average speeds for all these waves is known After an earthquake, the difference in arrival times at a seismograph station can be used to calculate the distance from the seismograph to the epicenter.

14. How is an Earthquake’s Epicenter Located? Time - distance graph showing the average travel times for P - a n d S - w a v e s . The farther away a seismograph is from the focus of an earthquake, the longer the interval between t h e a rr i v a l s o f t h e P - a n d S - waves

15. How is an Earthquake’s Epicenter Located? • • • Three seismograph stations are needed to locate the epicenter of an earthquake A circle where the radius equals the distance to the epicenter is drawn The intersection of the circles locates the epicenter

16. How are the Size and Strength of an Earthquake Measured? • – Modified Mercalli Intensity Map 1994 Northridge, CA earthquake, magnitude 6.7 • Intensity subjective measure of the kind of damage done and people’s reactions to it i s o s e i s m a l li n e s identify areas of equal intensity

17. How are the Size and Strength of an Earthquake Measured? • Magnitude Richter scale measures total amount of energy released by an earthquake; i n d e p e n d e n t o f i n t e n s i t y Amplitude of the largest wave produced by an event is corrected for distance and assigned a value on an open-ended logarithmic scale

18. Earthquake Magnitude

19. Destruction from Earthquake Representing response of vulnerable infrastructure during Earthquake

20. Soft storey failures observed in RC buildings

21. Typical failures observed in RC buildings.

22. Liquefaction Saturated material turns fluid Underground objects may float to surface

23. Land Slide Damage

24. Irregularities in Building as per IS 1893:2016 Plan irregularities : Torsional irregularity Re-entrant corners Floor slabs having excessive cut-outs or opening Out-of-plane offsets in vertical elements Non-parallel lateral force system

25. IRREGULARITY LIMITS Type of I r r e g u l a r i t y IS 1893:2016 Torsional i r r e g u l a r i t y dmax ≤ 1.5 dmin Torsional Irregularities Photograph representing Torsional Irregularities

26. IRREGULARITY LIMITS PRESCRIBED BY IS 1893:2016 Type of Irregularity IS 1893:20161 Re-entrant corners Ri ≤ 15% Re - entrant Corners Figure representing Re-entrant corners

27. Excessive cut - outs Figure representing Excessive cut-outs

28. Out of plane offsets in vertical elements Figure representing cut-of-plane offsets in vertical elements

29. Non Parallel L ateral Force System Figure Representing Nonparallel Lateral Force System

30. Vertical irregularities : Stiffness irregularity (Soft storey) Mass irregularity Vertical geometric irregularity In-plane discontinuity in Vertical elements resisting lateral force Strength irregularity (Weak storey) Floating or stub columns Irregularities in Building as per IS 1893:2016

31. IRREGULARITY LIMITS PRESCRIBED BY IS 1893:2016 Type of Irregularity IS 1893:20161 Weak Storey Si < 0.8Si+1 Stiffness Si < 0.7Si+1 Or Si < 0.8 (Si+1+ Si+2 +Si+3) Stiffness Irregularity Figure Representing Stiffness Irregularity in building

32. I RR E G U L A R I T Y L I M I T S P R E S C R I B E D B Y I S 1893 : 201 6 T y p e o f I r r e g u l a r i t y I S 1893 : 2016 1 Mass M i > 1 . 5 M i + 1 Mass Irregularity Figure Representing Mass irregularity in RC Building

33. Vertical Geometric Irregularity Figure Representing Vertical Geometric Irregularity

34. In plane Discontinuity in vertical E lements Resisting Lateral Forces In plane discontinuity in vertical elements

35. Floating Column Figure Representing Floating column Picture of Floating column